I believe we should upgrade Captain America's shield's durability to High 1-B, as it withstood a hammer strike from Odinforce Thor and was only dented (Avengers Vol 3 #63). It's consistently portrayed as needing this level of force to break, as the five times it's been destroyed were by the Molecule Man (Avengers Vol 1 #215), which is durability negation from High 1-B molecular smurf hax, by Doctor Doom with the Beyonder's power (Marvel Super Heroes Secret Wars #12), who is High 1-B, by the Beyonder's vibranium cancer (Captain America Vol 3 #21), which is durability negation and came from a wish with High 1-B potency, by Thanos with the Infinity Gauntlet (Infinity Gauntlet Vol 1 #4), who is Low 1-A, and by Cul Borson augmented with humanity's fear (Fear Itself Vol 1 #5), who is High 1-B.